1. Field of the Invention
The present invention relates to an electron multiplier for multiplying incident electrons by a series of dynodes.
2. Description of the Related Art
An electron multiplier is for multiplying electrons to produce current amplification. The electron multiplier is provided with an array of successively disposed dynodes. When an electron impinges on a first dynode in the array, the first dynode emits secondary electrons, which impinge on a second dynode, which further emits secondary electrons, and so on. In this way, electrons are successively multiplied by the series of dynodes. The electrons will be finally collected by an anode. Photomultiplier tubes are examples of electron multipliers wherein successive dynodes are provided between its photocathode and anode.
Conventionally, various types of electron multipliers have been proposed. However, as described below, conventional multipliers have an insufficient multiplication rate, that is, an insufficient rate, at which electrons are multiplied.
Japanese Patent Application Kokai No. 2-291656 describes an electron multiplier in which dynodes are arranged in a configuration resembling a Venetian blind as shown in FIG. 1. Electrons travel along various paths before falling incident on the dynodes. For example, an electron that travels along a path "b" will strike a dynode of a first row 101. However, an electron that travels along another path "a" passes between adjacent dynodes in the first row 101 to directly strike a dynode in the second row 102. As a result, the electron that travels along path "a" will not be multiplied by the dynode in the first row 101.